The present invention relates generally to fluid circuits, and more particularly to an integrated fluid control valve manifold of a fluid control system for powering vehicle accessories such as a cooling fan and a power steering unit.
Many vehicles include an engine cooling fan, with some being driven by a hydraulic motor. For economic reasons, it is known to provide an integrated fluid control circuit in these vehicles which includes both a fluid control circuit for operating an engine cooling fan, and a fluid control circuit for operating a hydraulic-assisted steering linkage. Such integrated fluid control circuits provide the necessary operational pressure for proper functioning of the fluid circuit with a single fluid pump. The use of a single fluid pump reduces costs associated with manufacturing the vehicle.
It is desirable to position the fluid components associated with the engine cooling fan in a series configuration with the fluid components associated with the hydraulic-assisted steering linkage. Such a series configuration creates a first pressure drop across the fluid components associated with the engine cooling fan and a second pressure drop across the fluid components associated with the hydraulic-assisted steering linkage. Such a configuration defines an integrated fluid control circuit wherein an output pressure on a fluid supply line of the single fluid pump fluctuates (i.e. rises and falls) as a function of the sum of the two pressure drops.
The pressure drop across each of the two groups of fluid components may vary widely depending on operating conditions associated with the vehicle. For example, on hot days the fluid pressure requirements associated with the engine cooling fan will increase. If during such a hot day the operator of the vehicle executes a steering maneuver that requires a large amount of fluid pressure (e.g. an abrupt, sharp turn), the sum of the two fluid pressure requirements may exceed the fluid pressure generating capabilities of the single fluid pump.
In such situations as described above wherein the fluid pressure requirements of the two groups of fluid components exceeds the pressure generating capabilities of the single fluid pump, it is desirable to give priority to the fluid components associated with the hydraulic-assisted steering linkage over the fluid components associated with the engine cooling fan. In particular, it is desirable to bypass fluid pressure around the fluid components associated with the engine cooling fan and direct the fluid pressure to the fluid components associated with the hydraulic-assisted steering linkage thereby reducing the speed of the engine cooling fan.
In addition, it is desirable to control the overall fluid pressure of the integrated fluid control circuit. In particular, it is desirable to provide fluid pressure necessary to operate the fluid components associated with the engine cooling fan and the hydraulic-assisted steering linkage while not exceeding the operative range of the pressure generating capabilities of the single fluid pump.
Still further, it is desirable to reduce the number of discrete fluid components included in the integrated fluid control circuit. In particular, it is desirable to provide a fluid valve manifold which can integrate one or more of the functions associated with the integrated fluid control circuit such as a pressure relief function and a bypass function into a single component. Additionally, it may be desirable to integrate other functions and/or components associated with the integrated fluid control circuit into the fluid valve manifold such as a fan motor associated with the engine cooling fan, and/or a flow control valve and a pressure relief valve associated with the hydraulic-assisted steering linkage. Such an integrated fluid valve manifold would provide for increased design efficiency and decreased manufacturing costs of the vehicle.
What is needed therefore is an apparatus and method that gives priority to the advancement of fluid pressure to the fluid components associated with the hydraulic-assisted steering mechanism over the fluid components associated with the engine cooling fan. What is further needed is an apparatus and method that controls on the overall pressure associated with the integrated fluid control circuit. What is also needed is a means to regulate and compensate flow as a function of engine speed. What is yet further needed is an apparatus and method that integrates one or more of the functions of the integrated fluid control circuit into a single fluid valve manifold.